1. Field of the Invention
The present invention relates to a display apparatus using an organic electroluminescence (EL) device (an organic light-emitting diode (OLED)), and more particularly, relates to a display apparatus using an organic EL device that can improve light utilization efficiency in the front direction.
2. Description of the Related Art
One problem concerning organic EL devices is that the light emission efficiency is low. In order to improve the luminance of an organic EL device, usually, it is necessary to take measures, such as increasing the luminous efficiency itself or passing a larger electrical current through the device. However, in the former, it is technically difficult to immediately improve the luminance, and there is a problem with the latter that the power consumption increases and degradation accelerates.
On the other hand, as measures to improve the luminance of an organic EL device while maintaining low driving current, a technique is known in which a convex lens is placed on the light extraction side so as to condense light, thereby improving the utilization efficiency of emitted light. Japanese Patent Laid-Open No. 2004-39500 discloses a structure in which a lens array composed of a resin is disposed on a silicon oxynitride (SiNxOy) layer that seals an organic EL device so that light collection efficiency in the direction of illumination can be improved.
In the organic EL device according to Japanese Patent Laid-Open No. 2004-39500, by condensing emitted light, light emitted in oblique directions is condensed in the front direction, and therefore, the luminance in the front direction is improved. However, the luminance in oblique directions is significantly decreased, resulting in a degradation in radiation angle characteristics, which is a problem.